People like The LowSpecgamer have made it their goal in life to run games on the weakest hardware and settings possible. Lazy Game Reviews entered this incredibly pixelated pantheon in a recent video about playing 2004's Doom 3 on a PC running Windows 98 and a 12MB Voodoo 2 graphics card. The results are nothing short of amazing:
As LGR explains, playing Doom 3 on a system like this takes some serious work. Windows XP and a 128MB graphics card are recommended for Doom 3, so it will only run on this setup after you tinker with the files and throw out everything but the kitchen sink, cranking all the graphics settings to minimum and even setting custom texture sizes. Even then, the final product suffers from serious framerate dips and looks like someone took a scouring pad to everything. Still, the fact that it's running at all is pretty remarkable.
If you'd like to replicate LGR's aptly titled "Potato Patch," you can find download and installation instructions here.